Lighting "experts" please respond, the kelvin issue - Page 2 - Orchid Board

Magnus A · #11 04-26-2009, 08:55 AM

There is NO scientific evidence that blue light give growth and red light gives flowers, in general!
When you look into the litterature you acctually can find reports of flower inhibition with red light!

This is something that most likely come from the people that grow marujana! This is a oneyear herb that grow over the summer and flower in the autumn when the natural light is more "red". Though thay have forgot about temperature differences AND that the plant flower when it is big enough. (Maybe due to something they grow

)

As long as you use modern full spectrum light the kelvin value is decided from some peaks in the spectral distribution. Use light with high CRI color rendering index which gives a natural look on colors.
People also grow orchids under Sodium lamps that has an extreme line spectra with more or less ONLY yellow light and they manage to flower their orchids.

As long as you give enough light the Kelvin number is of less importans. Water, air, nuitrition, temperature and season differences IS probably more of an issue!

I have used a set of 4 T5, 54W, 6500K, as ONLY source for my cabinet for over two years now and the orchids flower without problem! And they grow........

Ross · #12 04-26-2009, 09:15 AM

As many have stated here, a mix of lights seems to be a common practice. Many do this with no idea why (other than someone suggested it.) The 6500K lights will be fine for both growth and flowering. The 3000K tend to be a bit weaker in lumen output (but for all practical purposes nearly identical.) I happen to use a mix of 3-6500 to 1-3000 simply because I do a lot of photography of my plants and blossoms. The average 5000K output is perfect for photography. It nearly matches the color temperature of the sun at noon at the equator on a blue sky day. Most film (and digital imagers) are color-matched to 5000K but most computer monitors are setup for 6500K. Colors will appear a bit red on computer monitors when photographed under 5000K lighting. If one knows what's going on, it's simple to adjust images either direction, however.

I wouldn't wory about using either a mix or pure 6500K tubes when you replace them. A bigger issue is actual output (not advertized output or claims by vendors.) Only way to tell for sure is an accurate calibrated light meter. Take a few readings as the tubes "burn in" when first set up, then take readings a year later. You'll probably see a light drop off, as the tubes need to be replaced.

HereticHammer · #13 04-27-2009, 04:26 AM

What amazing responses. Thank everyone SO much. It really helps even though all may not agree.

I have come away with this thinking that I might just go with all 6700k lamps (the fixtures come with 3000k and 6700K but no offer for the 6500k mentioned more often in this thread so I hope 6700k is just as good.)

I guess I will need to add one 3000K for photography. That is irritating as I would prefer to go with all one bulb for simpicity if they grow and flower just as well under the higher kelvin but I guess the pictures would be a bit red if I just used 6700k.

I am just now getting into the photographing aspect (and I suck) so the information on taking pictures was very helpful.

Thanks again to everyone this thread has been so helpful.

billc · #14 04-27-2009, 04:32 PM

You could always take the plant out from under the lights and take the picture in natural light. That way you could keep the bulbs all the same. If you're like most of us, you have the plants all jammed in there, so to take a picture of a single plant, it has to be moved anyway.

Bill

quiltergal · #15 04-27-2009, 04:35 PM

That's true Bill, most of my photos are not taken on the rack either.

Magnus A · #16 04-27-2009, 06:44 PM

On many digital cameras you can set the white balance in Kelvin. I do not use this as my flourecense lack some wave length and I have founs some pink/red color are missing.
I try to use natural light for my photos whan I have the chance! I think I get the best result that way. And as someone pointed out, you often want to "stage" the plant before the photo so why not move it to better light

/Magnus

HereticHammer · #17 04-29-2009, 05:14 AM

Yes, I guess it is true that I will normally want to move them.

So I guess I should go with all 6700k lights?

phearamedusa · #18 04-29-2009, 09:30 PM

Both will work for you, go with which ever one you prefer. If you have a mixed selection now, that's fine too. When you re-lamp go with whatever is available, or that you like.

HereticHammer · #19 04-30-2009, 07:32 AM

Quote:

Originally Posted by phearamedusa

Both will work for you, go with which ever one you prefer. If you have a mixed selection now, that's fine too. When you re-lamp go with whatever is available, or that you like.

Since I'm no longer thinking of taking photos in there the main concern I have is being able to enjoy the orchidarium with the naked eye so I don't want bulbs that give a nasty looking color.

I would think that all 3000k would look bad. What would all 6700K look like?

phearamedusa · #20 04-30-2009, 10:38 PM

Quote:

Originally Posted by HereticHammer

Since I'm no longer thinking of taking photos in there the main concern I have is being able to enjoy the orchidarium with the naked eye so I don't want bulbs that give a nasty looking color.

I would think that all 3000k would look bad. What would all 6700K look like?

There will be a slightly whiter color for the 6700k, compared to the 3000k. Imagine a brite sunny day at noon(6700k), vs later in the day closer to sun set(3000k) say.